KHARIAN, Pakistan — Pakistan’s army is finally making significant gains in its campaign against Islamist militants, and some of the success can be traced back to unlikely sources: paintballs and bird calls.

Here, tucked in a forest, Pakistan’s military has built a sprawling base to train soldiers in how to fight small groups of terrorists. The National Counterterrorism Center Pabbi is one of a half-dozen training sites in Pakistan, but military leaders say 65 percent of the troops fighting militants in the northwest have been trained at this facility in Punjab province.

Earlier this month, the Pakistani military took The Washington Post on a rare public tour of the 2,500-acre facility, which opened in 2009 and resembles a hunting ranch on the scrublands of Texas.

The training, which includes some un­or­tho­dox methods, is designed to make Pakistani troops more proficient in face-to-face combat. Although the troops have gained experience fighting in harsh terrain over the past few decades, they are still largely geared toward a tank-on-tank war with arch rival India.

“After 9/11, it’s now a new world, and with this new world we are gearing up for our responsibility,” said Brig. Abrar Ali, commander of the center. “In our experience, this is not a battle with large forces. We have to learn how to fight in very small teams.”

A Pakistani soldier prepares for a training exercise at the National Counter Terrorism Center Pabbi in Punjab province. (Tim Craig/The Washington Post)

For years, U.S. lawmakers and generals have tried to get Pakistan’s military to shift its security posture to prioritize operations against Islamist militants sheltering in the country. To nudge it along, the Pentagon has given the Pakistani military $13 billion in reimbursements over the past 13 years for its counterterrorism efforts, according to a recent report by the Congressional Research Service. The State Department recently approved a $950 million arms sale to Pakistan, including 15 Viper helicopters, 1,000 Hellfire missiles and new radios.

But Pakistani commanders and troops say the training conducted at the National Counterterrorism Center Pabbi is what is really allowing them to gain the upper hand against Islamist militants. Since the army launched a major operation in June, soldiers have cleared most of North Waziristan. They are now trying to drive the extremists from their final hiding places in the Tirah Valley, in adjoining Khyber Agency, commanders say.

“These Taliban are dug in the caves, so you can’t do it by aerial bombardment,” said Javed Ashraf Qazi, a retired general and former head of Pakistan’s intelligence service. “You have to go in there and physically dislodge them.”

As many as 3,000 soldiers arrive each month for two dozen training scenarios, some of which are staged in a set made to look like a typical village in Pakistan’s Federally Administered Tribal Areas (FATA). The mock village includes nearly a dozen one- and two-story stone and mud structures, as well as a network of underground tunnels.

“This is a complete architectural rendition, from the interior to the exterior to the foxholes, of what you would see in FATA,” Maj. Nauman Mushtaq said as he led a reporter through a muddy tunnel that started in one house and ended in another.

Although the training includes some live-fire exercises, the army relies heavily on paintballs for its simulated war games.

A Pakistani soldiers carries ammunition used in training at the National Counter Terrorism Center Pabbi in Punjab province. (Tim Craig/The Washington Post)

On one part of the base, soldiers armed with paintball guns face off in a field about the size of a volleyball court. A unit in training will go through at least 2,000 paintballs.

During exercises, a soldier shot above the chest with a paintball is considered killed. Three or more hits below the waist mean ejection from the drill.

Maj. Khalid Waleed, who was overseeing the course, said Pakistani soldiers trained for battles in open farmlands along the border with India must now also become more comfortable with “close-quarters battles close to the ground.”

Another part of the base includes a mock two-story cave. A second-story window allows trainers and commanders to look into the cave. They use a computerized camera system and mannequins to fire paintballs at soldiers inside.

During a recent demonstration, three soldiers threw flash bangs before storming a cave. They took cover behind rocks as they spent several minutes battling their computer-aided opponent. By the time it was over, two soldiers had escaped unscathed; a third was scraping paint off his neck.

In another exercise, soldiers are taught how to fire from a moving truck. (Shoot the assailant closest to the vehicle first; it could be a suicide bomber.) Soldiers also practice how to rescue someone while still using both hands to fire their weapons. (Shoulders can carry a tremendous amount of weight.)

After years of casualties from insurgent ambushes, the military now sees the need for unconventional battle tactics. So soldiers also are learning how to conduct surprise offensive attacks.

In one exercise, a soldier hides in a tree in what looks like a large nest. He has been taught a variety of bird calls, one of which he calls out when he sees a potential target. Then, under the tree, soldiers concealed in a small pit covered with sticks and grass climb out and begin shooting.

“The terrorists don’t suspect us to use these tactics, so when we do, they are really badly trapped,” Ali said.

Lt. Col. Kashif Amin, who leads a cavalry regiment of 44 tanks based in the eastern city of Lahore, brought 400 soldiers for the training because their tanks are of little operational use in rugged North Waziristan.

“Especially for the younger soldiers, this is more challenging because they were trained for armored operations but will now be doing infantry,” Amin said.

The key to surviving as an infantry soldier in a place such as North Waziristan is knowing where to step.

Fake explosive devices are planted around the base, and they detonate when a soldier steps on them. One section of woodlands is littered with booby traps, including tripwires that if tugged cause wooden spears to swing out of trees. Soldiers also have to watch out for death traps, such as sharpened sticks at the bottom of a hole.

Still, Ali concedes that the military is battling an enemy who will probably always have some advantage when fighting in Pakistan’s tribal areas. He notes that many militants use the same stealth tactics that they or their fathers perfected as mujahideen fighters who resisted the Soviet occupation of Afghanistan in the 1980s.

“The only specialized training they need is how to make [bombs],” Ali said.